Build error with GCC-15 (class Poco::PriorityDelegate<TObj, void, true>’ has no member named ‘_pTarget’)

[stkw0]

Describe the bug
With GCC-15 Poco fails to build.

To Reproduce
Install GCC-15 pre-release or compile the latest GCC-15 from git and build Poco

Expected behavior
It builds correctly

Logs

/var/tmp/portage/dev-libs/poco-1.13.3/work/poco-poco-1.13.3-release/Foundation/include/Poco/PriorityDelegate.h: In member function ‘Poco::PriorityDelegate<TObj, void, true>& Poco::PriorityDelegate<TObj, void, true>::operator=(const Poco::PriorityDelegate<TObj, void, true>&)’:
/var/tmp/portage/dev-libs/poco-1.13.3/work/poco-poco-1.13.3-release/Foundation/include/Poco/PriorityDelegate.h:203:31: error: ‘class Poco::PriorityDelegate<TObj, void, true>’ has no member named ‘_pTarget’ [-Wtemplate-body]
  203 |                         this->_pTarget        = delegate._pTarget;
      |                               ^~~~~~~~
/var/tmp/portage/dev-libs/poco-1.13.3/work/poco-poco-1.13.3-release/Foundation/include/Poco/PriorityDelegate.h:203:58: error: ‘const class Poco::PriorityDelegate<TObj, void, true>’ has no member named ‘_pTarget’ [-Wtemplate-body]
  203 |                         this->_pTarget        = delegate._pTarget;
      |                                                          ^~~~~~~~
/var/tmp/portage/dev-libs/poco-1.13.3/work/poco-poco-1.13.3-release/Foundation/include/Poco/PriorityDelegate.h: In member function ‘Poco::PriorityDelegate<TObj, void, false>& Poco::PriorityDelegate<TObj, void, false>::operator=(const Poco::PriorityDelegate<TObj, void, false>&)’:
/var/tmp/portage/dev-libs/poco-1.13.3/work/poco-poco-1.13.3-release/Foundation/include/Poco/PriorityDelegate.h:277:31: error: ‘class Poco::PriorityDelegate<TObj, void, false>’ has no member named ‘_pTarget’ [-Wtemplate-body]
  277 |                         this->_pTarget        = delegate._pTarget;
      |                               ^~~~~~~~
/var/tmp/portage/dev-libs/poco-1.13.3/work/poco-poco-1.13.3-release/Foundation/include/Poco/PriorityDelegate.h:277:58: error: ‘const class Poco::PriorityDelegate<TObj, void, false>’ has no member named ‘_pTarget’ [-Wtemplate-body]
  277 |                         this->_pTarget        = delegate._pTarget;
      |                                                          ^~~~~~~

Screenshots
NA

Please add relevant environment information:
Linux 6.10.9
Poco 1.13.3

Additional context

[matejk]

I might have missed something, but I am not sure why it works on other compilers since the member is obviously missing.